The invention relates to an array or an apparatus and to a thermally conductive mass for the intermediate layer of such an apparatus.
“Heat source” according to the invention generally refers to a part of the apparatus or array containing at least one heat generating function element, for example a corresponding component or assembly. In particular, “heat source” according to the invention refers to an electric or electronic component, to a group of several such components, to an integrated circuit or also to an electric or electronic circuit containing one or more such components or circuits.
“Heat sink” according to the invention refers in general to a part of the apparatus or array according to the invention to which the heat from the heat source is to be transferred in the most optimum manner possible for the purpose of cooling, for example. In particular, “heat sink” according to the invention refers to a part of the apparatus or array according to the invention that serves to cool the electric or electric components or modules.
“Thermally conductive mass” according to the invention refers in particular to a material in a liquid, semi-liquid/viscous or solid state, which as an intermediate layer between the heat source and the heat sink ensures the optimum transfer of heat to the largest surface area possible, also if the corresponding surfaces provided for the transfer of heat (heat transfer surfaces) between the heat source and the heat sink are, for production reasons for example, not completely flat and/or are considerably rough.
Optimum cooling and heat dissipation is essential in electric and electronic components, especially in such components with a high power output or in components containing circuits or modules. Insufficient cooling can result in the destruction of the components and a reduced service life or life time of the corresponding circuit or module. In order to compensate for any uneven and/or rough areas on the adjacent heat transfer surfaces, for example the bottom or cooling surface of a component, an electric or electronic circuit or module and a heat sink (for example a passive or active cooler), normally an intermediate layer consisting of a thermally conductive paste is provided between said heat transfer surfaces. The disadvantage of this method is that after a certain period of operation, many known thermally conductive pastes lose a significant amount of their original thermal conductivity, so that the desired cooling effect of the respective component, circuit or module is lost. This effect is especially pronounced in such applications in which a constant change in the power dissipation and therefore a constant change in temperature occurs during operation, as for example during switching of an electric actuator. In this case, according to an underlying discovery of the invention, the temperature change at the transfer between the heat source (component, circuit or module) and the heat sink apparently causes a mechanical pump effect, with the effect that the thermally conductive paste, and in particular also the components affecting the thermal conductivity of said paste, is concentrated in a reduced surface area, for example in the edge area of the heat transfer surfaces between the heat source and the heat sink, resulting in a severe reduction of the actual surface available for the transfer of heat and therefore in a reduction of the cooling effect.
This problem is compounded by the factor of miniaturization and by ensuing increase of the power density particularly of power modules.
It is an object of the invention to demonstrate an array, arrangement or apparatus that eliminates these disadvantages while enabling the stable transfer of heat between a heat source and a heat sink over an extended period of operation.